This invention relates to surgical stapling apparatus, and more particularly to surgical stapling apparatus which is at least partly powered by a pneumatic system contained within the apparatus and which performs a sequence of operations such as tissue clamping, staple advancing, staple forming, and/or tissue cutting.
Surgical stapling apparatus is known in which tissue is first clamped, then fastened or ligated by means of staple-like metal fasteners or ligatures, and finally trimmed or cut by means of a knife prior to being released from the apparatus. Apparatus of this general nature includes ligating and dividing devices of the type shown, for example, in Noiles et al. U.S. Pat. No. 3,665,924 and Green et al. U.S. Pat. No. 4,086,926, and anastomosis devices of the type shown, for example, in Astafiev et al. U.S. Pat. No. 3,552,626.
Because of the difficulty and expense of cleaning and sterilizing surgical instruments between uses, there is increasing interest in and demand for instruments which are disposable after use in a single surgical procedure rather than permanent and reusable. And because of the greater convenience and ease of using self-powered instruments (i.e., instruments which are powered by a power supply contained within the instrument, as opposed to manually powered instruments or instruments which are powered by an external power supply such as a large free-standing cylinder of compressed gas connected to the instrument by a length of pressure hose), as well as the more uniform results typically produced by self-powered instruments (as compared especially to manually powered instruments), there is increasing interest in and demand for instruments which are self-powered or at least partly self-powered.
Heretofore, these two demands have been somewhat conflicting as applied to surgical stapling apparatus like that mentioned above. The relatively large forces required to clamp tissue, to cut tissue, and especially to drive staple-like fasteners or ligatures seemed to necessitate either a relatively high pressure gas supply such as carbon dioxide (vapor pressure approximately 800 p.s.i.g. at room temperature), or a relatively large pneumatic actuator. High pressure gas is difficult to work with in an instrument designed to be economically disposable and therefore preferably made of inexpensive materials in a relatively light construction. On the other hand, a large pneumatic actuator supplied with low pressure gas increases the size and bulk of the instrument, thereby increasing the amounts of material required to make the instrument and consequently increasing its cost. A large instrument may also be more difficult or even impossible to use in certain surgical procedures.
Another difficulty associated with low pressure pneumatic systems is that a low pressure gas supply of acceptably small size can store only a limited amount of energy. If a low pressure pneumatic system is to be used, it is important to utilize the limited energy stored in the gas supply of that system efficiently in order to provide an instrument with an economically acceptable life span prior to exhaustion of the gas supply. Even if the instrument is made so that the gas supply can be replaced, it is desirable to minimize the frequency with which this is required. Efficient use of the gas supply is especially difficult in an instrument for performing several functions such as tissue clamping, staple advancing, staple forming, and tissue cutting because different amounts of force are typically required to perform each function. If the pneumatic actuator is designed to produce the largest force required to perform any function, the actuator will generally be wasting considerable energy during performance of the other functions when less than that amount of force is required. This will substantially shorten the useful life of the gas supply.
Although it is desirable to perform most of the functions of the stapling apparatus automatically using the self-powering elements in the apparatus, it may also be desirable for the initial function to be at least partly manual. For example, if the initial function is tissue clamping, it is preferably initiated manually so that it can be performed slowly and precisely and the results inspected and corrected if necessary before the automatic self-powered portion of the operating sequence begins.
In view of the foregoing, it is an object of this invention to improve and simplify surgical stapling apparatus of the type which performs a sequence of functions and which is at least partly powered by a pneumatic system contained within the apparatus.
It is a more particular object of this invention to provide surgical stapling apparatus for performing a sequence of functions which is initiated manually and which is thereafter powered by an efficiently utilized low pressure pneumatic system contained within the apparatus.